Lead dioxide/manganese dioxide/sulfur
cure for polysulfide-bituminous com-
positions

ABSTRACT

1. A CURABLE, POLYMER BASED COMPOSITION COMPRISING, IN WEIGHT RATIO, 100 PARTS BY WEIGHT OFF AT LEAST ONE POLYSULFIDE POLYMER HAVING A PLURALITY OF TERMINAL GROUPS SELECTED FROM THE GROUP CONSISTING OF -SH AND -SSH, ABOUT 50 TO 300 PARTS BY WEIGHT OF BITUMINOUS MATERIAL, ABOUT 0.5 TO 10 PARTS BY WEIGHT OF ELEMENTED SULFUR, ABOUT 4 TO 20 PARTS BY WEIGHT OF LEAD DIOXIDE, ND ABOUT 0.5 TO 5 PARTS BY WEIGHT OF MANGANESE DIOXIDE.

United States Patent O LEAD DIOXIDE/MANGANESE DIOXIDE/SULFUR CURE FOR POLYSULFIDE-BITUMINOUS COM- POSITIONS John M. Pachuta, Trenton, N.J., assignor to Thiokol Corporation, Bristol, Pa.

No Drawing. Original No. 3,491,046, dated Jan. 20, 1970, Ser. No. 618,316, Feb. 24, 1967. Application for reissue Nov. 17, 1972, Ser. No. 307,734

Int. Cl. C08g 51/52 US. Cl. 260-28 Claims Matter enclosed in heavy brackets appears in the original patent but forms no part of this reissue specification; matter printed in italics indicates the additions made by reissue.

ABSTRACT OF THE DISCLOSURE Cured compositions containing polysulfide polymers and bituminous materials are provided which are resilient and do not revert or soften on heating. This combination of properties in the cured compositions is achieved by the use of a lead dioxide/manganese dioxide/sulfur cure system.

BACKGROUND OF THE INVENTION Compositions, such as cured sealant compositions, containing polysulfide polymers and bituminous materials are known (US. 2,910,922 and 3,238,165). Because of their good solvent resistance, such compositions are particularly useful in applications wherein the cured compositions are to come in contact with various solvent type materials such as gasoline and jet fuel. Such applications include, therefore, the sealing and coating of highways, parking lots, gasoline station aprons, air field surfaces and hanger decks. In order to be useful for such applications, the compositions must also be heat resistant in order to withstand the heat of the summer sun and/or the exhaust of jet engines, as well as resilient in order to be flexible enough to undergo expansion and contraction with changes in ambient temperature.

Curing agents which have been used to date for the curing of polysulfide polymer-bituminous material compositions include lead dioxide and manganese dioxide. The compositions cured with either or both of these curing agents, however, have a rather limited degree of utility since such cured compositions do not have the necessary combination of thermal stability and resilience properties which will allow for their widespread use in outdoor sealing or coating applications. Upon prolonged exposure to heat, such cured compositions revert or soften back and thereby lose the dimensional stability needed, for example, for joint sealing applications. The cured compositions may also be too hard or brittle for joint sealing or coating applications and therefore crack under stress of weight load or expansion and contraction of the sealed or coated structures upon exposure of such structures to changes in the ambient temperature.

SUMMARY OF THE INVENTION It has now been found that cured compositions containing polysulfide polymers and bituminous materials such as coal tar can be prepared for joint sealing and coating applications and which will be resilient and not revert back or soften upon exposure to prolonged heating, if there is used as the curing system for such compositions, a combination of lead dioxide, manganese dioxide and elemental sulfur. The curable composition of the present invention contain, per 100 parts by weight of polysulfide polymer therein, about 50 to 300 parts by weight of bituminous material, about 0.5 to 10 parts by weight of elemental sulfur, about 4 to parts by weight "ice of lead dioxide, and about 0.5 to 5 parts by weight of manganese dioxide.

DESCRIPTION OF THE PREFERRED EMBODIMENT The polysulfide polymers which may be used in the novel compositions of the present invention are organic polymeric materials which are liquid, i.e., pourable at room temperature, about 25 C., and which contain recurring polysulfide linkages, i.e. (S,,)--, in the polymeric backbone, wherein n is, on the average, about 1.5 to 5. The polymers contain a plurality of SH or SSH groups through Which the liquid polymers may be oxidatively cured to form solid elastomers. Such polymers include those which have --SH terminals as are described in US. 2,466,963; polymers which have SSH groups as are described in copcnding application Scr. No. 583,480 filed Sept. 30, 1966, now US. Patent No. 3,331,818 in the name of E. R. Bertozzi and polymers which have blocked SSH groups as are described in copending application Ser. No. 302,724 filed Aug. 16, 1963 in the name of E. R. Bertozzi and now abandoned. The preferred of these polymers are those having a molecular weight of about 500 to 12,000. The most preferred of such polymers are those having a molecular weight of about 500 to 4,000, since such polymers allow for the most efficient cure times. Structurally, the polymers may be represented by the formula I" '1 F l 1 x\-Rs1, It's. A A l: L n ly A ias. r le'sfl u' wherein The polymers having SH terminals would have the structure I F f 'l 1 its RS, ltS.-II it i: .LL .J

' Ltir). l.,

wherein the average numerical value of all the zs and Z""s is about 1.5 to 2 and R, R, x, y and n are all as defined above.

The polymers having SSH terminals would have the structure 'l l' irss RS.--R'S.' SH SH l i it HSS Rex F n'sa sn Jrl wherein R, R, z, z, x, y and n are all as defined above. Each of the various types of these polymers can be used either alone or in combination with one another in the novel compositions of the present invention.

The elemental sulfur which may be used according to the teachings of the present invention can be any of "spas."

the commonly available forms of monomeric or polymeric elemental sulfur, or other chemicals or chemical compositions which would provide elemental sulfur under the normal conditions of use for compositions of the type described herein. Such sources of elemental sulfur would include, therefore, rhombic, monoclinic and amorphous sulfur. As indicated above, useful compositions may be prepared according to the present invention which may contain about 0.5 to parts by weight of the elemental sulfur per 100 parts by weight of polymer. In order to obtain the most useful compositions which will provide a desired balance of relatively fast cure time for the composition and good physical properties in the cured systems, the preferred amount of sulfur to be used is about 1 to 3 parts by weight. For the same reasons the preferred amounts of lead dioxide and manganese dioxide to be used, per 100 parts by weight of polymer, is about 10 to 13 parts by weight of lead dioxide and about 1 to 2 parts by weight of manganese dioxide.

The bituminous materials which may be used in the compositions of the present invention are preferably of a coal tar derivation and include all of such materials disclosed in US. 2,910,922 and 3,238,165. In order to assure a reasonable fast cure of the composition, the bituminous material should have a relatively neutral to basic pH, i.e., about 6 or higher. More acidic materials can be neutralized to achieve the desired pH range.

About 50 to 300 parts by weight of the bituminous materials may be used per 100 parts by weight of polymer. The bituminous materials of a coal tar derivation are the preferred of such materials because relatively high loadings of such materials, i.e., above 50 parts by weight per 100 parts by weight of polymer, can be used in the compositions without leading to the formation of cured compositions which will revert or soften back under prolonged heat exposure. The most preferred of such bituminous materials of a coal tar derivation are those having a viscosity within a range of seconds Saybolt Furol at 77 F. to 150 seconds Saybolt Furol viscosity at 210 F., and more preferably a viscosity range of 200 to 700 seconds Saybolt Furol viscosity at 77 F. as tested by ASTM D-88-44. Materials having a higher viscosity may be thinned out with higher boiling plasticizers or solvents. and materials of a lower viscosity may be used where the more volatile nature of such materials would not interfere in the performance of the cured composition.

In addition to the components mentioned above, the compositions of the present invention may also contain various other adjuvants commonly employed in elastome, based sealants without detracting from the usefulness of the compositions for the herein described purposes. Such adjuvant materials should be essentially inert with respect to the components mentioned above.

The compositions may contain, therefore, one or more materials useful as fillers, pigments, and/or reinforcing agents such as carbon black, clays, slate flour, limestone, calcium carbonate, asbestine, aluminum oxide, titanium dioxide, zinc sulfide, silicon dioxide, magnesium silicate, iron oxide and rayon floc. In general the use of these materials tends to decrease the elongation and increase the Shore hardness, toughness and tensile strength of the cured polymer systems. Up to about 200 parts by weight of such materials may be used per 100 parts by weight of polymer.

Plasticizers may also be used in the presently claimed compositions, particularly in combination with the more viscous bituminous materials. Such plasticizers would include chlorinated biphenyls, dibutyl phthalate, dipropylene glycol dibenzoate, di (butoxy-ethoxy-ehtyl) adipate, di (butoxy-ethoxy-ethyl)formal, tricresyl phosphate and butyl benzyl phthalate. The plasticizers should preferably be aromatic in nature to insure physical compatability with the bituminous components of the compositions. Up to about 0 to 100 parts by weight of the plasticizers y 6 used per 100 parts by weight of polymer.

Adhesive additives, such as organo silane compounds, and the phenolic and epoxy resins may also be used in amounts of up to about 10 parts by weight per parts by weight of polymer.

Other additives that may be used, depending on the application, are cure accelerators, ultra violet light stabilizers, thixotropic agents, cure retarders and leveling agents.

The compositions of the present invention may be used cemmercially in the form of a two-part system. Such twopart systems are those in which the chemically reactive components thereof are stored in separate packages and mixed together, to achieve the desired cure reaction iust prior to use. This type of system is the most commonly employed in the curable polymer based sealant arts at this time and usually involves the storage, for example, of the curable polymer and curing agent in separate packages until it is desired to use the system. In the case of the present systems, therefore, where it is desired to maintain the components in packaged form for prolonged periods of time it is desirable to place the polymer in one package and the curing agents, PhD; and MnO in another package. The sulfur, furthermore, should not be packaged with the PbO For long term storage purposes the novel compositions of the present invention, therefore, may be packaged as a two-part system wherein one part will contain polymer, sulfur and some or all of the bituminous material, and the second part will contain the P1302, MnO and the remainder of the bituminous material. If no bituminous material is used in the second part, a plasticizer may be used to facilitate the eventual dispersion of the PbO and M in the polymer-bituminous material part of the system. The other optional adjuvant materials discussed above can be incorporated in various combinations of proportions in either of the two parts of the system.

The following examples are merely illustrative of the novel compositions of the present invention and are not intended as a limitation upon the scope thereof.

EXAMPLES A series of two-part formulations were prepared. In each case the Part A component contained bituminous material, curing agents and fillers, and the Part B component contained the polysulfide polymer, sulfur, Where sulfur was used, and more bituminous material or plasticizer. The Part A and Part B components of the formulations were then mixed together in an effort to obtain a cure thereof. Suitable tests were conducted on the cured formulations to point out the patentable features of the claimed compositions. The initial cures, in all cases were conducted at room temperature, about 20 C., for 24 hours. After the initial cures certain physical properties of some samples of the cured systems using non-destructive test procedures were noted. The same samples were then heat aged for seven days at 158 F. and then certain physical properties of the aged systems were also observed and evaluated.

The non-destructive testing of the cured and aged samples involved a penetration test and a resilience test. Those tests were conducted in accordance with ASTM D5-52 and an ASTM D-2l7-52T cone was used for the penetration tests. The penetration test is a measure of the degree of cure of the sample and the tests results are reported in centimeters. Preferred materials are those exhibiting penetration test results of the order of 0.05 to 0.15 centimeters. The cured compositions with the better physical properties exhibit the lower test values in this test procedure. When tested for resilience, cured composition should preferably have a minimum resilience of 90%. The cured compositions with the better resilience properties will exhibit the higher test values in this test procedure.

A third test procedure used to evaluate the cured compositions of the present invention is a destructive type test procedure wherein the test sample is destroyed B E III duri g the testing procedure. This is called a flow test Example 7 8 Q and is conducted on cured samples in accordance with Pm A WM Si g a 4 X 1 2 X test B g};io ig Agfi g-iifl L 11D 10 110 10 Sample 5 it a a a A separate set of samples is used in this test procedure. i r 7 7 This test procedure involves first curing a sample at 2 g i 2 room temperature for 24 hours and then heating it for pm It (pm-1,51 Weight): n hour at 212 F. to see Whether or not the cured g ly l f g g lvmr h gt 7;; sample will soften or revert back under such test condi- 1o 3-", "wfi gggr' gg' a tions and flow. Materinll and Bituminous Material iii 55 a 55 The compositions tested and results obtained are shown ,,ftiliiftfififittt,at; 'ciir' iii 'rbi'biidiiiyiii 3 ll'l Th6 fOllOWll'lg tablets: room temperature:

Penetration tom.) 0.05 0. 06 0.05 0.05 1 Resilience(percentL.ddt 1 1 t J6 J6 ll? 06 P iysical properties a ter a i iona iea' aging TABLE I [or seven days at 158 F.:

Penetration (en1.) 0. 08 0.08 0.07 0.16 Example 1 2 3 Resilience iporcentl 03 04 04 79 Part A (parts by weight): Examples 7 to 10 illustrate the [act that only a small amount of sulfur Bituminous Matel'lal I. 51 31 31 is needed to prevent softening or reverting back of compositions cured Bitum nous Material IL. 20 with a combination of M I10: and P b0 2. Even under relatively mild heat; Asbeslmt 325 (mfigmslum 510C916)- 6 5 F 20 aging conditions, the composition of Example 10, which did not contain g MT (Carbon 37 37 37 sullur, softened or reverted back. Pbo 13 13 13 4 4 W Polysulfido Polymer l- 50 50 liolyfulfiil folytrlrlierillflhngyhuni. 5U 50 50 I l i roe er 05 or t Flwlth 54% 01 e p em 65 66 66 1. A curable, polymer based composition comprising,

6mm? Eu] 3 in wei ht ratio Pb steal ro erties O e at ila ite m e aiuw X00 parts by weight of at least one polysulfid; fpolyngler one m on em. 0.16 0.45 0.07 ii ecte roi'n e m up h 80 13 90 having a plurality of teirriiml gio 56b 50 t 300 Physical propertigs atteg 1afidrgigonal heat gioup iOHSIStmg 0f SH and S 8 Out 0 aging orseven aysa 8 Pe t ti Q22 Q17 0.10 parts welght of bltuljnlnous matte I Resilience (percent) e3 46 93 about 0.5 to 10 parts by weight of e ementa su ur,

about 4 to 20 parts by Weight of lead dioxide, and Bituminous I is a high boilin coal tar distillate oil havin a 8:1 bolt Ugiversail visc i t oi 70ttol140 s econds at 160 F. i h g y 1 about 0.5 to 5 parts by weight of manganese CllgXldE. d

itum nous snmet y no hthalene coaltariract on avin adisti i 1am, range M255 to 0 O p g 2. A curable composition as in claim 1 in w ich sai Polysulfide polymerlisnliquld polysulfide polymer having essentially {in polysulfide polymer has -SH terminal groups. figgg g HswtHtOcHiocinssmcmtocHlOCZHtSH with 4% 3. A curable composition as in claim 1 in which said C mg. ti ll lolystiiillfidetl oltymer lllIsiscalllicgibinpglgsigfidse)pog gngilaivn bituminous material 13 Of 2. C021] tar derivation. fly esrncure i s 2 2 v with1% branching, 2 4 5 l l 4. curable, polymer based composition conipiising,

in weight ratio, 40 100 parts by weight of at least one polysulfide polymer The tests conducted in Examples 1 and 2 indicate that having a plurality of groups, polysulfide polymer-bituminous compositions cured with about 5 to 3 parts by weight f bituminous mate. lead dioxide alone, or a combination of lead dioxide and rial of Coal derivation, manganese dioxide, are too soft and not resilient enough. about 0 to 10 parts by Weight f eiomentai lf r, h p t n tested In a p 3 Much was F n about 4 to 20 parts by weight of lead dioxide, and with a combination of lead dioxide, manganese dioxide about 5 t 5 parts by weight of manganese dioxideand sulfur, however, had a high degree of resilience and 5 A curable, polymer based composition i i was not too soft initially and did not soften on heating. in Weight ratio,

100 parts by weight of at least one polysulfide polymer TABLE II having a plurality of -SH groups, Example 4 5 6 about 50 to 300 parts by weight of bituminous material P tA m b i ht of coal tar derivation,

i i g itg no no 110 about 1 to 3 parts by weight of elementatsulfur,

0 1 gigiflfamorphous diatoma 21 21 21 about 10 to 13 parts by weight of lead dioxide, and SEE b1a.k eats stints i4 14 14 55 about 1 to 2 parts by weight of manganese dioxide. Asblefitlne 325 7 7 7 P w Pl i;: i.l.l% 1g 1. anal? References Cited 8! i Z i i llzoly uigige gggg'eri g; The following references, cited by the Examiner, are

oysu o o ymer 80/20 mixture by weight of Bitumb of record in the patented file of this patent or the original IIBIOISflLiTHItIBII'lH-I I and Bituminous 55 55 55 patent.

8 8 a Ph Eilementalsulfurf "f 1 1 1 UNITED STATES PATENTS dti tt figittiiietittrt 0 0B 0 06 0 07 3331 P k 2 791 ene ra on em. Payne 2 2 Resilience (percent) 98 97 05 o Phyisiea} propertigs aftetr1a5rggltional heat; 69 3 ,318 7/1967 260'-79.l

ag ng 0! SBVBl'l 83 55 .2 memo, .120 1/ 968 B n zzi 260 79.1 Resilience (percent) n 23 a5 93 3,505,254 4/1970 Kidwell 26079.l

2 I 5 Flowaltfll' 1 11011! heating at 212 F--- U 3 540 9 1 11 197 sh 26O 28 r l badl 70 0W8 y. gitnminoiiistMiligilailogls a coal tar pitch having a Ring and Ball ALLAN LIEBERMAN Pnmary Examlner 50 8D mg po I1 0 Examples 4 and 5 show that cured compositions formulated according P R- MICHL, Asslstant Exammer to the present invention have the desired resilience properties and do not soften or revert back upon exposure to prolonged heating. Example 6 U S C1 X R demonstrates that although a composition cured with MnOz and sulfur i may have desirable properties initislly, that such compositions will 260-79 1 soften or revert back under prolonged heating. 

1. A CURABLE, POLYMER BASED COMPOSITION COMPRISING, IN WEIGHT RATIO, 100 PARTS BY WEIGHT OFF AT LEAST ONE POLYSULFIDE POLYMER HAVING A PLURALITY OF TERMINAL GROUPS SELECTED FROM THE GROUP CONSISTING OF -SH AND -SSH, ABOUT 50 TO 300 PARTS BY WEIGHT OF BITUMINOUS MATERIAL, ABOUT 0.5 TO 10 PARTS BY WEIGHT OF ELEMENTED SULFUR, ABOUT 4 TO 20 PARTS BY WEIGHT OF LEAD DIOXIDE, ND ABOUT 0.5 TO 5 PARTS BY WEIGHT OF MANGANESE DIOXIDE. 